Your Eco re-powers The National Trust
The National Trust, in partnership with certified B Corp™ Your Eco, has delivered a transformative solar PV expansion at Heelis Head Office in Swindon—setting a new benchmark for sustainability in heritage environments. The project increased the rooftop solar array from 60kWp to a cutting-edge 344kWp system, supporting the Trust’s Net Zero by 2030 ambitions.
Repowering Heelis – Heritage Meets Innovation at National Trust HQ
Your Eco’s solution combined technical innovation with respect for architectural integrity. The installation involved 765 bi-facial DMEGC 450Wp panels, three SolarEdge SE90K inverters, and 385 S1000 optimisers, providing advanced panel-level monitoring, safe DC management, and rapid fault detection. Eight roof areas were fitted with a bespoke mounting system to suit the building’s steel structure and wind loading requirements. Despite challenging winter weather and restricted labour hours, the project was delivered on schedule with minimal disruption.
Sustainability was at the heart of the project. Significant legacy system elements—traywork, cabling, and inverters—were recycled, reducing waste and supporting the Trust’s conservation ethos. The new system operates on a behind-the-meter, self-consumption model, with additional rooftop, ground-mounted, and containerised structures. Total installed DC capacity is 343.80kWp, with peak AC output of 266.64kW and expected annual generation of 346.99MWh—equivalent to saving 1,680 tonnes of CO₂ each year.
A CT Modbus monitoring system enables real-time performance tracking, ensuring most electricity is used on-site and reducing grid reliance. Electricity costs are lowered to around 3.3p per kWh, with the project forecast to deliver a 38% annual ROI and a four-year payback period. The National Trust also benefits from Clean Energy Cashback Feed-in Tariff (FiT) eligibility, with both generation and export meters installed.
This project demonstrates that commercial solar can enhance, rather than compromise, heritage values—delivering measurable environmental and economic benefits while respecting the character of a landmark building.
